ABSTRACT
Problematic soils in civil engineering are known as soils with properties that cannot be safely and economically used for the construction of civil engineering structures without adopting some stabilization measures. This research work is to evaluate the sub-grade and sub-base characteristics of problem soils using fly ash and rice husk ash, cement and lime as stabilising agents. Fly ash is the by-product produced by coal-burning electricity generating power plants. Rice husks are the natural sheaths that form on rice grains during their growth. Guided by these objectives to sample and determine the sub-grade and sub-base material properties of Benin-Auchi Road problem soils.
Soil were taken from depth of 100- 150 (mm) was stabilized with 0, 5, 10, 15 and 20% of rice husk ash, fly ash, lime and cement and combination of cement and fly ash, cement and lime and cement and Rice husk ash. The sample was subjected to preliminary test, specific gravity, particle size analyse and Atterberg Limits for identification and classification purposes as well as compaction and California bearing ratio (CBR).The index properties of the natural soil showed that soil belong to A-7-5 soil is silty sand.. Silty soil extends in large stretches and construction of pavements and other structures on such type of soils is a great problem.
The liquid limit (LL). Plastic limit (PL) and Plasticity Index (PI) for the natural soil sample are 37.02, 16.72 and 20.30% respectively. The laboratory results indicate decrease in maximum dry density except for lime increased 15 and 20%, liquid limit and increase in optimum moisture content and plastic limit of sample. At 0% soaked CBR for the soil sample was 14.14. For Cement, it increases from 124.28 to 160.87 lime increase from 7.23 to 11.56 fly ash increase 7.06 to 25.92. Rice husk ash increase from 9.19 to 15.44. The higher value of CBR that is 115.04 was obtained at 5% cement 15% of lime. The results of the findings shows that the geotechnical properties of the stabilized soil was significantly improved but still unsuitable for base/sub-base material in road construction.
